90% of the games I watch seem to go to extra innings, and are decided by bench/really crappy players, so my favourite would be a close game decided by a top-tier player doing something awesome in late innings. Just feels right if a great player makes the telling contribution. I hated the 2005 World Series where an important at-bat was Blum vs Astacio, that sucked.

Or any game my g/f watches with me. Every single time she watches one (which is pretty much never) something wild happens. For example, her first ever game was the OAK/TEX in 2004 game where Francisco threw a chair into the crowd.

Walking up the ramp and seeing the field in any stadium for the first time is great, like seeing the ocean for the first time when you're a kid.Also, when the national anthem is performed in a baseball stadium feels special for me every time.

As far as plays on the field... a rundown always cracks me up since it's such a common play in little league but less typical in the bigs.

Watching at home: I love when the everyone in the dugout snubs a player after a HR, or when a rookie gets his first hit. Then they jump on him. The BoSox did it to Ortiz when he finally hit a HR to break out of his slump.